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LIBRARY OF CONGRESS. 

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UNITED STATES OF AMERICA. 



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Hppletons' 1bome IReatong Boofce 

EDITED BY 
WILLIAM T. HARRIS, A.M., LL. D. 

UNITED STATES COMMISSIONER OF EDUCATION 



DIVISION I 

Natural History 



APPLETONS' HOME READING BOOKS 



THE EARTH AND SKY 



A PRIMER OF ASTRONOMY 
FOR YOUNG READERS 



BY 
1/ 



EDWARD S. HOLDEN, Sc. D., LL. D. 




NEW YORK 

D. APPLETON AND COMPANY 

1898 



18607 



Copyright, 1898, 
By D. APPLETON AND COMPANY. 



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TWO oOFitj) fitGtIVEO. 



INTRODUCTION TO THE HOME BEADING 
BOOK SEEIES BY THE EDITOR. 



The new education takes two important direc- 
tions — one of these is toward original observation, 
requiring the pupil to test and verif y what is taught 
him at school by his own experiments. The infor- 
mation that he learns from books or hears from his 
teacher's lips must be assimilated by incorporating it 
with his own experience. 

The other direction pointed out by the new edu- 
cation is systematic home reading. It forms a part of 
school extension of all kinds. The so-called " Univer- 
sity Extension " that originated at Cambridge and Ox- 
ford has as its chief feature the aid of home reading by 
lectures and round-table discussions, led or conducted 
by experts who also lay out the course of reading. 
The Chautauquan movement in this country prescribes 
a series of excellent books and furnishes for a goodly 
number of its readers annual courses of lectures. The 
teachers' reading circles that exist in many States pre- 
scribe the books to be read, and publish some analysis, 
commentary, or catechism to aid the members. 

Home reading, it seems, furnishes the essential 
basis of this great movement to extend education 



vi THE EARTH AND SKY. 

beyond the school and to make self -culture a habit 
of life. 

Looking more carefully at the difference between 
the two directions of the new education we can see 
what each accomplishes. There is first an effort to 
train the original powers of the individual and make 
him self-active, quick at observation, and free in hia 
thinking. Next, the new education endeavors, by the 
reading of books and the study of the wisdom of the 
race, to make the child or youth a participator in the 
results of experience of all mankind. 

These two movements may be made antagonistic 
by poor teaching. The book knowledge, containing as 
it does the precious lesson of human experience, may 
be so taught as to bring with it onlv dead rules of 
conduct, only dead scraps of information, and no 
stimulant to original thinking. Its contents may be 
memorized without being understood. On the other 
hand, the self -activity of the child may be stimulated 
at the expense of his social well-being — his originality 
may be cultivated at the expense of his rationality. 
If he is taught persistently to have his own way, to 
trust only his own senses, to cling to his own opinions 
heedless of the experience of his fellows, he is pre- 
paring for an unsuccessful, misanthropic career, and 
is likely enough to end his life in a madhouse. 

It is admitted that a too exclusive study of the 
knowledge found in books, the knowledge which is 
aggregated from the experience and thought of other 
people, may result in loading the mind of the pupil 
with material which he can not use to advantage. 



EDITOR'S INTRODUCTION. V1 [ 

Some minds arc so full of lumber that there is no 
space left to set up a workshop. The necessity of 
uniting both of these directions of intellectual activity 
in the schools is therefore obvious, but we must not, 

in this place, fall into the error of supposing that it is 
the oral instruction in school and the personal influ- 
ence of the teacher alone that excites the pupil to ac- 
tivity. Book instruction is nut always dry and theo- 
retical. The very persons who declaim against the 
book, and praise in such strong terms the self -activity 
of the pupil and original research, are mostlv persons 
who have received their practical impulse from read- 
ing the writings of educational reformers. Very few 
persons have receive;! an impulse from personal con- 
tact with inspiring teachers compare;! with the num- 
ber that have been aroused by reading such books as 
Herbert Spencer's Treatise on Education. Rousseau's 
Emile. Pestalozzi's Leonard and Gertrude. Francis 
TV. Parker's Talks about Teaching, G. Stanley 
Hall's Pedagogical Seminary. Think in this connec- 
tion, too, of the impulse to observation in natural sci- 
ence produced by such books as those of Hugh ATiller, 
Faraday. Tyndall. Huxley. Agassiz. and Darwin. 

The new scientific book is different from the old. 
The old style book of science gave dead results where 
the new one gives not only the results, but a minute 
account of the method employed in reaching those re- 
sults. An insight into the method employed in dis- 
covery trains the reader into a naturalist, an historian, 
a sociologist. The books of the writers above name;! 
have done more to stimulate original research on the 



viii THE EARTH AND SKY. 

part of their readers than all other influences com- 
bined. 

It is therefore much more a matter of importance 
to get the right kind of book than to get a living 
teacher. The book which teaches results, and at the 
same time gives in an intelligible manner the steps of 
discovery and the methods employed, is a book 
which will stimulate the student to repeat the ex- 
periments described and get beyond them into fields 
of original research himself. Every one remem- 
bers the published lectures of Faraday on chemistry, 
which exercised a wide influence in changing the 
style of books on natural science, causing them to 
deal with method more than results, and thus train 
the reader's power of conducting original research. 
Robinson Crusoe for nearly two hundred years has 
aroused the spirit of adventure and prompted young 
men to resort to the border lands of civilization. A 
library of home reading should contain books that in- 
cite to self-activity and arouse the spirit of inquiry. 
The books should treat of methods of discovery and 
evolution. All nature is unified by the discovery of 
the law of evolution. Each and every being in the 
world is now explained by the process of development 
to which it belongs. Every fact now throws light on 
all the others by illustrating the process of growth in 
which each has its end and aim. 

The Home Reading Books are to be classed as 
follows : 

First Division, Natural history, including popular 
scientific treatises on plants and animals, and also de- 



EDITORS INTRODUCTION. [ x 

scriptions of geographical localities. The branch of 
study in the district school course which corresponds 
to this is geography. Travels and sojourns in distant 
lands ; special writings which treat of this or that 
animal or plant, or family of animals or plants ; any- 
thing that relates to organic nature or to meteorol- 
ogy, or descriptive astronomy may be placed in this 
class. 

/Second Division. Whatever relates to physics or 
natural philosophy, to the statics or dynamics of air or 
water or light or electricity, or to the properties of 
matter ; whatever relates to chemistry, either organic 
or inorganic — books on these subjects belong to the 
class that relates to what is inorganic. Even the so- 
called organic chemistry relates to the analysis of 
organic bodies into their inorganic compounds. 

Third Division. History, biography, and ethnol- 
ogy. Books relating to the lives of individuals ; to 
the social life of the nation ; to the collisions of na- 
tions in war, as well as to the aid that one nation 
gives to another through commerce in times of peace; 
books on ethnology relating to the modes of life of 
savage or civilized peoples ; on primitive manners 
and customs — books on these subjects belong to the 
third class, relating particularly to the human will, 
not merely the individual will but the social will, 
the will of the tribe or nation ; and to this third 
class belong also books on ethics and morals, and 
on forms of government and laws, and what is in- 
cluded under the term civics, or the duties of citi- 
zenship. 



X THE EARTH AND SKY. 

Fourth Division. The fourth class of books in- 
cludes more especially literature and works that make 
known the beautiful in such departments as sculpture, 
painting, architecture and music. Literature and art 
show human nature in the form of feelings, emotions, 
and aspirations, and they show how these feelings 
lead over to deeds and to clear thoughts. This de- 
partment of books is perhaps more important than 
any other in our home reading, inasmuch as it teaches 
a knowledge of human nature and enables us to un- 
derstand the motives that lead our fellow-men to 
action. 

Plan for Use as Supplementary Reading. 

The first work of the child in the school is to 
learn to recognize in a printed form the words that 
are familiar to him by ear. These words constitute 
what is called the colloquial vocabulary. They are 
words that he has come to know from having heard 
them used by the members of his family and by his 
playmates. He uses these words himself with con- 
siderable skill, but w r hat he knows by ear he does not 
yet know by sight. It will require many weeks, 
many months even, of constant effort at reading the 
printed page to bring him to the point where the 
sight of the written word brings up as much to his 
mind as the sound of the spoken word. But patience 
and practice will by and by make the printed word 
far more suggestive than the spoken word, as every 
scholar may testify. 

In order to bring about this familiarity with the 



EDITOR'S INTRODUCTION. x i 

printed word it has been found necessary to re-en- 
force the reading in the school by supplementary 
reading at home. Books of the same grade of diffi- 
culty with the reader used in school are to be pro- 
vided for the pupil. They must be so interesting 
to him that he will read them at home, using his time 
before and after school, and even his holidays, for 
this purpose. 

But this matter of familiarizing the child with the 
printed word is only one half of the object aimed at 
by the supplementary home reading. He should 
read that which interests him. He should read that 
which will increase his power in making deeper 
studies, and what he reads should tend to correct his 
habits of observation. Step by step he should be 
initiated into the scientific method. Too many ele- 
mentary books fail to teach the scientific method be- 
cause they point out in an unsystematic way only 
those features of the object which the untutored 
senses of the pupil would discover at first glance. It 
is not useful to tell the child to observe a piece of 
chalk and see that it is white, more or less friable, 
and that it makes a mark on a fence or a wall. Sci- 
entific observation goes immediately behind the facts 
which lie obvious to a superficial investigation. 
Above all, it directs attention to such features of the 
object as relate it to its environment. It directs at- 
tention to the features that have a causal influence in 
making the object what it is and in extending its 
effects to other objects. Science discovers the recip- 
rocal action of objects one upon another. 



xii THE EARTH AND SKY. 

After the child has learned how to observe what 
is essentia] in one class of objects he is in a measure 
fitted to observe for himself all objects that resemble 
this class. After he has learned how to observe the 
seeds of the milkweed, he is partially prepared to 
observe the seeds of the dandelion, the burdock, and 
the thistle. After he has learned how to study the 
history of his native country, he has acquired some 
ability to study the history of England and Scotland 
or France or Germany. In the same way the daily 
preparation of his reading lesson at school aids him 
to read a story of Dickens or Walter Scott. 

The teacher of a school will know how to obtain 
a small sum to invest in supplementary reading. In 
a graded school of four hundred pupils ten books of 
each number are sufficient, one set of ten books to be 
loaned the first w^eek to the best pupils in one of the 
rooms, the next week to the ten pupils next in ability. 
On Monday afternoon a discussion should be held 
over the topics of interest to the pupils who have 
read the book. The pupils who have not yet read 
the book will become interested, and await anxiously 
their turn for the loan of the desired volume. Another 
set of ten books of a higher grade may be used in the 
same way in a room containing more advanced pupils. 
The older pupils who have left school, and also the 
parents, should avail themselves of the opportunity to 
read the books brought home from school. Thus is 
begun that continuous education by means of the pub- 
lic library which is not limited to the school period, 
but lasts through life. W. T. Harris. 

Washington, D. C, Nov. 16, 1896. 



AUTHOK'S PBEFACE. 



This book is intended as the first of a series 
of three or more volumes all treating of astron- 
omy in one form or in another. All of them 
are suited for reading in the school and in the 
home, and they will have failed of their object 
if they do not inspire young readers to under- 
take simple astronomical observations on their 
own account ; and if they do not, at the same 
time, suggest the spirit in which such observa- 
tions must be made, and reflected upon, to be 
truly fruitful. 

The earliest teaching of astronomy must be 
closely joined to the teaching of geography. 
What is already known about the earth will 
serve as a stepping-stone to a knowledge of 
the planets ; and, conversely, the little we 



xiv THE EARTH AND SKY. 

know of the planets will serve to throw light 
upon the constitution of the earth, and spe- 
cially upon its past and future history. Any 
child who is old enough to study geography is 
not too young to begin to grasp astronomical 
ideas, and to observe simple astronomical phe- 
nomena. 

The lessons of a child's first years, whether 
given at school or less formally through read- 
ing at home, are necessarily extremely simple. 
He should first be led to making an inventory 
of the visible universe — sun, moon, planets, 
comets, nebulae, stars. His books will describe 
these objects, and he must be led by slow de- 
grees toward verifying the descriptions by his 
own observations. 

If a constellation is figured in his book he 
must be made to see that the figure exists in 
the book because the constellation exists in 
the sky. It is not so simple as it appears to 
fix in a child's mind the fundamental fact that 
it is Nature which is true and the book or the 
engraving which is a true copy of it. "It 
says " — is the snare of children as well as of 



AUTHORS PREFACE. xv 

their more sophisticated elders. The vital 
point to be insisted on is a constant reference 
back from words to things. After the things 
are understood we may go back to words 
again, and we can then restate the matter in 
hand in briefer, apter, and more technical 
forms. 

The early studies of a child should be util- 
ized to lay the foundations of future advances. 
For example, the child should have his atten- 
tion directed, almost at the beginning, to some 
of the more striking constellations — to the 
Great Bear, to Orion, to the Pleiades. Dur- 
ing the whole lifetime of the child the naming 
of the constellations should go on. It is not 
so much that these names are of any great 
importance, though to know them is a source 
of real pleasure. But in tracing their outlines 
through the sky, by the eye, the mind becomes 
intent on allied matters, and the thoughts 
reach out to better things. 

Very many children will take a lively in- 
terest in the identification of stars and in tra- 
cing the course of the planets among the con- 



xvi THE EARTH AND SKY. 

stellations ; and this interest deserves to be 
fostered for its ultimate, as well as for its im- 
mediate, results. The delight of discovery is 
hardly less poignant to the child who has 
really observed for the first time that the 
stars in their courses really move about the 
pole from east to west, than to an astronomer 
of maturer age who makes some real step to 
advance his science. 

Early in the child's life his attention 
should be directed to the observation of the 
moon's face, of her phases, and of her motions. 
After the unassisted eye has done its part the 
use of a common field glass will open a new 
world. Galileo was not better equipped. An 
opera glass, a watch, a straight stick for a 
gnomon, or for testing the allineations of stars 
or planets, bits of colored glass for looking at 
the sun (using care in this matter), terrestrial 
and celestial globes, if they are to be had — 
these are the simple pieces of apparatus that 
the child should be encouraged to successively 
acquire and utilize. 

It is very important to introduce such aids 



AUTHOR'S PREFACE. xv ii 

slowly, one by one. The eye should be faith- 
fully employed before the opera glass is used. 
Thoroughness is a scientific (and a moral) vir- 
tue which a child can not acquire too early ; 
and the simplest beginnings of astronomical 
acquirement may be used to impress the habit 
on a child's character. 

Not only should observations be made as 
thoroughly as possible with the means at hand, 
but they should be recorded neatly, accurately, 
and exhaustively. The child should feel a re- 
sponsibility for what he records, and he should 
authenticate his pages or his drawings by his 
signature. A signed page will soon come to 
mean to him an observation that has been care- 
fully and correctly made, and that can be de- 
pended upon ever after. 

The observation of the morning and even- 
ing stars will serve as an introduction to the 
mapping of the apparent path of a planet 
(Mars, Jupiter, or Saturn) among the stars. 
The revolution of the moon will suggest the 
origin of the month, and thus may introduce 
some consideration of the calendar — a knotty 



xx THE EARTH AND SKY. 

steadily cultivated. The circles exist, first of 
all, in the heavens, and the book or the globe 
only exist because the circles are there. The 
ground idea of an eclipse is very simple if it 
is studied out of doors with real shadows. 
Afterward the drawings of a book will mean 
something real. 

The power of conceiving geometric rela- 
tions of the sort can be wonderfully culti- 
vated even in young children. Just as de- 
scriptive-geometry gives the very best training 
to advanced students of mathematical form, so 
this habit of representing geometrical relations 
in the mind is of prime importance to the 
beginner in astronomy. 

All the early teachings of children in Na- 
ture studies should, in general, be directed 
mainly to training their eyes to observe cor- 
rectly and to leading their minds to genuine 
reflection. What they learn of the facts of 
astronomy is of comparatively little account. 
The real matter is so to use the universe as to 
train each small mind to observe, to register, 
and to reflect. 



AUTHOR'S PREFACE. xx i 

Astronomy is especially fitted to serve this 
end, and it has been my endeavor in these 
volumes to utilize it to the best advantage of 
the child. 

New York, January, 1898, E. S. H. 



BRIEF ANALYSIS OF THIS BOOK. 



The volume is written as a conversation with a young 
lad. He is first shown how he may know for himself that 
the earth is not flat, though it certainly appears to be so. 
The next step is to show him that he may know that the 
earth is, in fact, round ; and that it is a globe of immense 
size. Its situation in space is next considered, and the 
child's mind is led to some formal conclusions regarding 
space itself. The sun and the moon are next treated, and 
the child is encouraged to observe the moon's phases, and 
shown exactly how he may best do it. This leads him to 
inquire why it is that the bright part of the moon changes 
its shape from night to night. He is put into a position 
to solve this problem for himself. The motion of the stars 
in their courses is next considered, and the child learns 
for himself that the earth turns round once in every day. 
It is believed that nothing here presented is too difficult 
for a young child to comprehend, and that the bases of 
scientific habits are laid down in a manner not to be mis- 
understood. 



CONTENTS. 



CHAPTER PAGE 

I. — The earth is not flat 1 

II. — The earth is round . . . . . . .9 

III. — The earth is a large globe . . . . . 17 

IV. — The earth in space 29 

V.— The sun . ^ . 38 

VI.— The moon . . . . . . . .47 

VII. — Why the bright part of the moon changes its 

SHAPE FROM NIGHT TO NIGHT 62 

VIII. — The stars in their courses — the earth turns 

round once in every day 74 

Plates of the sun, moon, planets, eclipses, me- 
teors, OBSERVATORIES, AND TELESCOPES . . 97 

XXV 









3 



THE EARTH AND SKY. 



CHAPTER I. 

THE EARTH IS ISTOT FLAT. 

Well, Master Frank, as you wish to learn 
something about astronomy, suppose we begin 
our first lesson. Astronomy is the science that 
tells us about the sun and the moon and the 
stars as you know already. 

But let us first talk a little about the 
earth. By and by we will talk about the stars. 
They are so very far off that we shall have 
some trouble to understand much about them. 
But we are living on the earth, and if we 
take pains we can find out a great many things 
about it. And what we find out will be in- 
teresting, too. 

Of course, you know that the earth is not 
really flat, though it certainly seems to be so. 






2 THE EARTH AKD SKY. 

It is really a huge ball, larger than anything 
you can imagine. You know that very well. 
But just knowing a thing is not enough. You 
must be able to say why you know. And that 
is not so easy. Taking pains and knowing why 
is pretty much all of science, and we might as 
well begin at once. 

I am going to ask you what you would do 
if I should introduce you to one of those little 
Eskimo boys that Lieutenant Peary found liv- 
ing on the flat ice in the arctic regions, and if 
I should say, "Now, Master Frank, here is a 
little boy of your own age who doesn't believe 
the earth is round at all. He speaks English, 
you know. And he is quite a bright boy, too. 
But he says the earth looks flat, and that it 
must really be flat " — what would you say to 
that ? How would you make him understand ? 
It will not be of the least use to tell him that 
all the people you know — papa, mamma, Aunt 
Clara, and your school-teacher — say that it is 
certainly so. 

He would probably say that these are very 
nice people, but that his eyes tell him that the 






THE EARTH IS NOT FLAT. 3 

earth looks flat. And shall he not trust his 
own eyes ? It will be of no use to say that he 
is stupid, and that he has got to believe what 
he is told. He is not stupid. He just does 
not know. And we have got to teach him. 

If we really know about it ourselves, we 
can do that by taking enough pains. But I 
think it will take quite a long time. Suppose 
we try it together. You could do it by your- 
self, no doubt. But perhaps we can do it 
more quickly if we both try. Recollect that 
this little Eskimo boy will not believe a single 
thing unless we can make him see with his 
own eyes that it is just as we say it is. 

There is one thing that we might do that 
would certainly convince him, though it would 
take a long time and would cost more money 
than we could possibly spare. We might 
make him sail quite round the world in a ship ? 
and come back to us here and tell us where he 
had been, and how he happened to be back 
where he started from. Just let us see how 
we might do this if we only could. 

In the first place, we should have to go to 



4 THE EAftTH AND SKY. 

the bank and get a great deal of money — as 
much money as would be needed to hire one of 
the ocean steamships, with her captain and all 
her men, for three or four months. And we 
should have to buy coal for the engines and 
food for the men, and all sorts of fittings for 
the ship. If a rope should break, or be lost ■ 
overboard, there must be a new one all ready 
to put in its place. 

Then we should have to go down to a sea- 
port and find a steamer to hire. No doubt one 
could be found. There are always plenty of 
them. We should have to tell the captain just 
what we wanted him to do. " The whole ship 
and all the men on it are wanted, Captain, just 
to take this little Eskimo boy round the world 
and to bring him back to New York. 77 

" But why in the world, 77 the captain would 
probably say, " do you want this little boy to 
take this long voyage of twenty -five thousand 
miles ? 77 " Oh, just to prove to him that the 
world is, in fact, round and not flat. 77 I sup- 
pose the captain would be astonished, don 7 t 
you? But he would have to go, all the same. 



THE EARTH IS NOT FLAT. 




6 THE EARTH AND SKY. 

We should put our boy on the ship, and lie 
would sail away out of the harbor, past Sandy 
Hook lighthouse to the east. 

You and I can follow on the map the 
way the ship would go. In the first place 
they would sail to the east, across the Atlan- 
tic Ocean, through the Straits of Gibraltar, till 
they got into the Mediterranean Sea; and 
then nearly the whole length of this sea to the 
Suez Canal ; and down the Red Sea to the 
Indian Ocean ; and round the end of India to 
the Pacific ; and, always sailing toward the 
east, across the Pacific Ocean and around 
Cape Horn into the Atlantic again, and finally 
back to Sandy Hook once more. They would 
have to stop for more coal and for fresh pro- 
visions at quite a number of places, and they 
could hardly arrive at Sandy Hook before 
three or four months. 

In the meantime you and I might amuse 
ourselves in many ways, and almost forget our 
ship, and the little boy. But finally there 
would come news that the ship was coming in, 
and we should go down to the wharf to meet 



THE EARTH IS NOT FLAT. 




8 THE EARTH AXD SKY. 

it. What a lot of things our little boy would 
have seen in his long voyage ! What a wise 
boy he would have become ! He would cer- 
tainly know one thing, at any rate. He would 
know that you could sail quite round the 
world, and that it was so large that it took 
something like four months to make the 
voyage. 

But this would be a very costly way to 
teach a single boy, and to teach him so little, 
after all. There are much better ways, and. 
we shall have to think about them. 



OHAPTEE II. 



THE EARTH IS KOTJ]N T D. 



Instead of sending our little Eskimo boy 
on a long voyage round the world to prove 
to him that the earth is not flat, we can do 
better. We can all three go to the seashore 
and watch the ships sailing away and think 
about what we see. 

This picture shows us what we might 
really see in any harbor like New York, or 
Boston, or San Francisco. The ships are sail- 
ing away to foreign countries. Some of the 
ships are near and some far off, and there 
must be other ships, beyond the edge of the 
sea, that we can not see at all. They sailed 
away this morning and are out of sight now. 
They are already beyond the edge of the sea. 
There is a name for that line where the sea 



10 



THE EARTH AND SKY. 



and the sky meet. It is called the Iwrizon line 
— the hor-i'-zon, with the accent on the i. 

It is the line where the sea and the sky 




Ships sailing out of a harbor. The more distant ships look 
smaller. The hull of each ship disappears first, as she sails 
away. The uppermost sails are seen longest. 

meet. You see that it is a line. At least it 
looks like one. 

Now let ns look at the ship that is nearest 
to ns. What do you see ? (Look at the pic- 
ture, which is a true one.) You can see the 
whole of this ship, with all her masts, her 



THE EARTH IS ROUND. H 

three sails on each mast, and her flag. It is a 
French flag in the picture — three upright 
bands of red, white, and blue really, though 
the colors are not given. Those are the 
French colors. You can see the hull of 
the ship— the wooden ship herself, that is 
— and her tall masts. She is so near the 
shore where we are that we can see her 
plainly. 

Now look for a moment at the ship next to 
her. This one is farther away and you do not 
see her so plainly. She looks smaller, too. 
And the third ship looks smaller still, and so 
on. That is something to remember. The 
farther away a ship, or a house, or a locomo- 
tive, is the smaller it looks. You know that 
already, of course, and so does every Eskimo 
boy, though very likely lie has never said it in 
plain words like that. The second ship is so 
far away that she looks smaller. But we can 
see the whole of her. The hull is there, and 
the masts and the flag, too. 

Now let us look at the third ship in the 
picture. Recollect that the picture is a true 



12 THE EARTH AND SKY. 

one. Real ships near a real shore would look 
just so. A photograph of ships would be a 
true picture, and it would show them just as 
this drawing does. The third ship looks 
smaller than the second one because it is far- 
ther away. And the hull of this ship is not 
to be seen. We know that the hull is there, 
of course. 

Let us look at the fourth ship now. It 
is smaller, of course, and not so plain. But 
you can not see the hull at all. The sails 
are there and the masts, but where is the 
hull ? Of course the hull is really there. All 
ships have hulls, and this one has a hull, 
surely. But what is the reason we can not 
see it ? 

Something has come between our eyes and 
the hull of this fourth ship. And you must 
notice that while we can see her topsails, the 
lower ones are partly hidden too. At the left- 
hand side of the picture there is another ship 
almost out of sight. You can not see her hull. 
Her lower sails are quite out of sight, and even 
the middle sails are nearly hidden. It looks 



THE EARTH IS ROUND. 13 

exactly as if she were going down over the 
farther side of a hill. 

If we should stay here and watch all these 
vessels we should find that pretty soon the 
fifth one would vanish entirely. She would 
seem to slip down over the farther side of 
some hill. She would go beyond the horizon 
line — the line which is just at the meeting of 
sea and sky. Soon she would be quite out of 
sight. Her middle sails would vanish first, and 
then her topsails, and she would soon be quite 
gone and there would be nothing to watch. 

We might w r atch the next ship in the same 
way ; and the same things would happen, in 
just the same order. The middle sails would 
vanish first, and then the top ones ; and she 
would be gone too. It would be the same for 
every one of the ships. When a ship is near 
we can see the whole of her. We can see her 
hull, her masts, and the three sails on each 
mast. As she sails away from us we see less 
and less of her. 

The hull disappears below the horizon line 
first ; then we lose sight of her lower sails ; 



14 THE EARTH AND SKY. 

next the middle sails disappear ; at last the 
upper sails are seen no longer, and the ship has 
vanished from our sight. These things will 
always happen, in just this order, if you watch 
for them. The tallest things will be seen long- 
est. The sails that are nearest to the water 
vanish first. The tallest sails vanish last. No 
matter when you come to the seashore you 
will always see this happen. 

If the sea were really flat, as it looks, these 
things would not be so. The hull of a ship is 
the biggest part of her, and on a flat sea it 
would be seen longer than any other part. 
But if the sea is rounded, like a part of the 
outside of a huge globe, things would be as 
they are in this next picture. 

Suppose we were up in the tower, at the 
left-hand side of this picture, looking out over 
the sea, and that there were quite a number of 
ships, just as the picture show T s them. If we 
took a long stick, like a cane, and held it level 
w r e might look along it. If the cane were sud- 
denly to grow miles long it would look like 
the straight line in the top of the picture. The 



THE EARTH IS ROUND. 15 

cane would be perfectly straight, and we 
should be looking along it. The ships would 
be sailing over the water just as in the picture. 




This picture shows a part of the curved surface of the sea. A 
person at the top of the tower will see the whole of the mid- 
dle ship in the picture, but only parts of the two ships to the 
right. The further away a ship is, the less he will see. 

The nearest ships would be seen completely. 
The whole of each near ship would be seen. 
Some of the far-away ships would be hidden, 
as in the picture, and only the highest parts of 
these far-away ships would show. The lowest 
parts would be hidden, so that if the sea were 
really curved like a globe and not flat, just the 
same things would happen that really do 
happen. 

The first picture showed exactly what can 
be seen any day, by any one, anywhere at the 
seashore. The ships do vanish just that way 
— the lower parts first, the higher parts next, 
the highest parts last. The next picture shows 



16 THE EARTH AND SKY. 

that if the sea was curved and not flat these 
very things would happen just as they do hap- 
pen. If the sea were rounded the far-away 
ships would glide away behind the rim of the 
world. 

We have found a reason for what happens. 
If the sea is really rounded the rim of it will 
hide ships that sail behind it, just as ships are 
really hidden in fact. Even a little Eskimo 
boy can understand that. Let us give him a 
short time to think about it. 



CHAPTEE III. 

THE EAETH IS A LARGE GLOBE. 

There is a very simple experiment which 
you can try, Master Frank, the next time you 
go bathing in the ocean. If you try it, it 
will prove that the surface of the sea is round. 
Or you can try it in a large lake. A river will 
not do. Most rivers are so narrow that the 
earth does not bend enough out of a straight 
line in the little distance across them from 
shore to shore. 

You can try it in the ocean on a perfectly 
calm day when there are no waves. Stand on 
the beach first, just at the edge of the water, 
and look out to sea. If there is a boat — a row- 
boat — a mile or two out, you can see the whole 
of it — that is, all of it that is out of water, of 
course. Your eye is some three feet above the 
ocean level. 

17 



18 THE EARTH AND SKY. 

Now wade into the sea until the water is 
nearly up to your chin and look for the boat. 
You will only see a part of her ; the sea has 
curved in between you and the boat and hid- 
den the lower parts of the hull. The higher 
parts can easily be seen still, but the lower 
parts are hidden. 

So long as your eye is close to the water 
the rounding of the sea will hide something. 
The water curves up like a little hill in front 
of you. When you stand on the beach at the 
edge of the water you are able to look over 
the top of the hill, just as if you were in the 
tower in the last picture. (Turn back and 
look at it, please.) 

If a man were as tall as the tower his eye 
would look out over the ocean along the line 
that is drawn all across the picture. If he 
were very short, so that his eye were at the 
foot of the tower, he would see the whole of 
the first ship, part of the second one, and only 
the top of the masts of the third one. 

You can prove this for yourself if you will 
hold the straight edge of a card above the left- 



THE EARTH IS A LARGE GLOBE. 19 

hand side of the picture. Above it. And you 
must hold the card so that one corner of it 
touches the very foot of the tower — that is 
where the man's eye is now — and so that the 
bottom edge of the card just touches the water 
somewhere near the second ship. 

The man at the foot of the tower looks 
along a line which is just the same as the line 
of the card. The rim of the ocean is for him 
about where the second ship stands. Every- 
thing nearer to the tower than the second ship 
he sees very well. Everything farther off is 
partly cut off from his sight. I think this will 
be plain. And even our Eskimo boy can be 
made to understand this if you explain it to 
him slowly and patiently. 

You may try to answer another question. 
Suppose a man to be in the tower so that his 
eye were in the very top of it, what would he 
see? Take the card again; put it above the 
picture so that its left-hand lower corner is 
just at the very top of the tower, and move its 
lower edge till the card just touches the sea, 
about halfway from the third to the fourth ship. 



20 THE EARTH AND SKY. 

The rim of the sea for the man in the top 
of the tower is where the lower edge of the 
card touches the sea — just about halfway be- 
tween the third and fourth ships. He will see 
the three nearer ships very well, the farther 
ones he will only see partly. I think your 
Eskimo friend can understand this, too. Let 
us give him something a little harder to think 
about. 

This picture shows things as they would 
be if we three could travel up a high mountain 
with no other mountains round it to shut out 
the view. It might be a mountain in the midst 
of the sea. Now, if we first went to the very 
top of it (where there is a little s in the pic- 
ture) and looked around, what should we see ? 
Remember there is nothing to hide the view — 
no other mountains nor hills. We should be 
able to look off a long, long way. If the moun- 
tain were a mile high we could see the earth 
in every direction for about a hundred miles. 

We could see just as far in one direction as 
in every other. Just as far to the south as to 
the north ; just as far to the east as to the west. 



THE EARTH IS A LARGE GLOBE. 



21 



There is nothing to hide the view. The largest 
circle, a a a (you must find these three a's), is 
the horizon line for us at the top at s. Every- 
thing in the sky we can see. And we can also 




This picture shows that people at different heights have different 
horizons. A person at the top of the mountain will have the 
largest horizon. He will see the most of the surrounding 
country. A person on the side of the mountain will see less 
country, and a person on the plain at the foot of the moun- 
tain will see the least of all. 



see everything on the surface of the ground 
between the circle a a a and the foot of the 
mountain. 

If we could take a rope a hundred miles 
long and fasten one end of it to the very sum- 
mit of the mountain, at s, and carry the other 
end down to the ground ; and if we could al- 
ways keep the rope straight like the two lines 



22 THE EARTH AND SKY. 

sa and ^ou the left- and right-hand sides of 
the picture ; and if then we could walk along, 
always keeping the rope straight, we should 
find that we were walking along a circle, like 
the line marked "Horizon at the top of the 
mountain " in the picture. 

Of course, we can not really have a rope a 
hundred miles long, and if we could it would 
be entirely too heavy to carry ; but you can 
imagine it, can't you ? The three lines, s a, s a, 
s a (a different a each time), will show how 
the rope would look if only we could make it 
and stretch it out. 

If we should climb down to the place 
marked c (on the left-hand slope of the moun- 
tain) we should find that we had quite a new 
horizon and one not nearly so wide. At the 
place c we should look along the line c e' to the 
earth. The point a and all the circle a a a 
would be quite hidden. You can imagine a 
rope stretched from c to e\ and a boy walking 
round the circle e' e o — "horizon halfway up." 

And if we should climb down to the very 
foot of the mountain (where the letter h is in 



THE EARTH IS A LARGE GLOBE. 23 

the drawing ; you must find it, please), the new 
horizon would be much smaller. It is marked 
on the smallest circle " horizon on the plain." 
Once more you can imagine a shorter rope 
here, like h i in the picture, and a boy walking 
around the circle marked " horizon on the 
plain." Of course we should make the boy 
walk round the whole circle, not only round 
the half circle drawn in the picture. You see 
that it is only a half circle ? The other half of 
the circle is hidden behind the earth itself in 
the picture. The earth is not transparent — 
you can not see through it — and we are obliged 
to draw the picture that way. 

A man's eyes are about five feet above the 
ground, and his horizon line is less than three 
miles distant. When he climbs a mountain a 
mile high he can see in every direction about a 
hundred miles. That is one of the reasons why 
men take so much trouble and run such risks 
to climb high mountains. The views they get 
are splendid and very wide. 

Your dog's eyes are only about a foot from 
the ground. Did you ever think how much 



24 



THE EARTH AND SKY. 



he misses, just because lie is not tall like you ? 
The next time you are out in an open field, get 
down on all-fours, like a dog, and look about 
you and see how small the world has become. 
If you stand up in the center of a very large 
field you can see about two miles in every di- 
rection ; and your father, who is taller, can see 
nearly three miles. And the people on the 
top of a mountain a mile high can see about 
one hundred miles. 

Look at the last picture once more, please. 
If you were at the very top of the mountain, 
at s, you would see about you in every direc- 
tion, and the rim of your world would be the 
line marked " horizon at the top of the moun- 
tain." You could see just 
as far toward the north as 
toward the south. Your 
horizon line would be a 
circle then. 

If you w T ere at i^and 
looked to the north you 
could see to N and no farther ; if you looked 
to the south you could see to 8 and no farther ; 




THE EARTH IS A LARGE GLOBE. 



25 



if you looked east or west you could see to 
Eov JTand no farther. That circle, NE8W, 
would be your hori- 
zon line. Half of it 
is shown in the pic- 
ture of the mountain. 
Your horizon line 
on the earth, whether 
you are at sea or on 
a large plain, is al- 
ways a circle. If you 
look up in the sky 
there is no horizon 
there at all. You 
can look off as far 
as the moon and 
the stars. These are 
facts which you can 
observe at any time 
and anywhere on 
the earth. The earth 
itself is of such a shape that everybody's horizon 
is always a circle. So the earth must be a globe, 
and we must be living on the outside of it. 




school globe that shows the 
round earth with its continents 
and oceans. The lines are 
drawn on the globe for conven- 
ience to show the latitudes 
and longitudes of cities. Of 
course there are no such lines 
on the real earth. 



26 THE EARTH AND SKY. 

We know that the earth is a very large 
globe too. If we travel round it on a steam- 
ship, like the little Eskimo boy, w r e can count 
up at the end of each day how many miles we 
have sailed, and add up all the miles of all the 
days when we get home again. We should 
find that it was about twenty-five thousand 
miles round the earth where it is largest. 

Or, we might start from New York on a 
railway train, and go directly west some three 
thousand miles to San Francisco, and by steam- 
er to the eastern side of Siberia, and across 
Siberia by railway and wagon to Europe, and 
across Europe to France by railway, and back 
from France to New York by steamship. You 
should trace out this journey on the map. If 
we should count up all the miles of all the 
days (some eighty days) of this journey we 
should find, just as before, of course, that it 
was some twenty-five thousand miles round the 
earth. 

So that the earth is not only a globe but it 
is also a very large globe indeed. If you were 
to try to walk from New York to San Fran- 



THE EARTII IS A LARGE GLOBE. 27 

cisco, only three thousand miles, it would take 
nearly a year for you to do it. And it is more 
than eio;ht times farther round the whole 
globe. If it were all dry land you might walk 
round it in seven or eight years. That would 
be a long walk. And the earth is certainly a 
large globe, not a small one. 

Now is not all this very plain ? Of course 
you understand it ; but I mean would it not be 
easy to explain all this to any Eskimo boy who 
wanted to know about such things ? You 
would need to thoroughly understand it your- 
self and, to be very plain and very patient, 
and you could explain it to anybody — to an 
Eskimo boy, or to anybody at all. It doesn't 
matter what anybody says about this now; 
you know it for yourself. If you have a new 
hat or a new gun you can lose them by acci- 
dent, but you can't lose knowing a thing that 
you have once really learned. 

Before we stop speaking about the earth I 
want to tell you one thing more. Very many 
men have sailed round the earth, and thou- 
sands and thousands of men have wandered 



28 THE EARTH AND SKY. 

over nearly every bit of dry land on it. Every 
one of these men everywhere has noticed that 
the earth was quite separated from every other 
globe. It does not touch the sun ; it does not 
touch the moon ; it does not touch the stars. 
On the contrary, they seem to be very far off 
from every part of the earth ; and so they are. 
This large round earth of ours is quite by 
itself ; it touches nothing else in the sky. Just 
think about this a little, and recollect that you 
are a small and very nice boy on the outside 
of an exceedingly large globe, and that this 
globe is all by itself. It does not rest on any- 
thing. It touches nothing. Even the moon is 
very far away, and we are nearer to the moon 
than to anything else in the heavens. 



CHAPTER IT. 

THE EARTH L^T SPACE. 

It is certain that we live on an earth that 
is round, and that is exceedingly large. If 
the seas were turned into dry land, so that 
you could walk all round the earth, it would 
take seven or eight years for you to do it. 
And this round earth is all by itself. It does 
not touch the sun, the moon, the stars, but 
is, in fact, far away from any one of them. 

You stand on the solid earth itself. Now 
what else is around you ? Well, there is first 
the air that you breathe. You know it is there, 
although you can not see it. You can feel it 
when you breathe it. Is there any other way 
that you can feel it ? Yes — of course the wind 
that blows against your face is nothing but 
air moving. When there is no wind you 

29 



30 



THE EARTH AND SKY. 



hardly know that there is any air at all, but 
when the wind blows there is no doubt about 
it. Some one has made a kind of a picture 
of the earth and the air, which is copied 
here. 

The earth is the black globe in the mid- 
dle and the air is the circles in the draw- 




ing. In the picture thay have given only a 
part of the earth, leaving you to imagine the 
rest. You can do that, can't you ? And you 
must think of the earth as a globe with air 
all around it. In the picture they have called 
the air "atmosphere," which is the scientific 
name for it. It really means vapor-spliere, 
that is, the sphere or globe that holds the 
vapor, the fogs, the clouds, and the air. 



THE EARTH IN SPACE. 31 

This is not a real picture, like a photo- 
graph, which shows just how the earth and its 
atmosphere would look to a person on the 
moon for example ; it is rather more like a 
memorandum which you make in a book. It 
helps you to remember how things really are. 
You remember the memorandum, but you must 
see the things themselyes "in your mind's eye.'' 

You know you Ye got a way to see with 
your mind, and you can see that way whether 
your eyes are open or shut. It will make no 
difference at all. You can imagine them. You 
must imagine the earth, then, Master Frank, to 
be a huge globe. You are a little speck some- 
where on its outside surface. All around the 
earth is a thick layer of air, and you are in 
the air just as if you were standing in inyisible 
water. The ocean water is yisible, and if you 
get into it you are wet. If you go to the bot- 
tom of it you are drowned. 

There is an ocean of air all around the 
earth, oyer the land just as well as oyer the 
sea ; and you and I and all of us are walking 
about at the bottom of this ocean of air. We 



32 THE EARTH AND SKY. 

live at the bottom of the ocean of air just as 
crabs live at the bottom of the ocean of water. 
The ocean of water is not so very very deep 
— not often more than three or four miles 
deep. 

The ocean of air over our heads is very 
much deeper. It is more than a hundred 
miles deep ; more than a hundred miles high 
above our heads. The birds fly about in it 
just as the fish swim in the ocean, and we walk 
about on the bottom just as crabs walk about 
on the bottom of the ocean. 

What do you suppose is above the air? 
Well, there is nothing above it. As you 
climb up the mountain there is less and less 
air to breathe. Try to do it sometime and 
you will find out ! When you have climbed 
up two miles or so, there is so little air that 
climbing gets to be very hard w r ork indeed. 

If you still go on climbing for another 
mile you will be three miles high. It is very 
cold there, and the rocks are always covered 
with snow. The air is very thin. There is 
scarcely enough of it to breathe. It is diffi- 



THE EAETH IN SPACE. 33 

cult to take even a few steps. The highest 
mountains in North America, in Hawaii, and 
in Switzerland are about three miles high. 
In India there are a few huge mountains, four 
and five miles high. 

Balloons have been sent up with men in 
them to nearly six miles, but sometimes the 
men have died for want of air, though now 
we have learned how to be safe even so high 
as this. Even the birds do not fly so high as 
this. Balloons with no men in them have 
been sent up as high as ten miles ! Think of 
that ! It is horribly cold at that height, and 
there is scarcely air enough to float the bal- 
loon. Of course you know that a balloon 
floats in the air exactly as a cork floats in the 
water. 

The higher you go in the air the less air 
there is. By and by there is no air at all, 
and the space is empty. All around the 
earth is its bedquilt of air (we may call it a 
bedquilt because it keeps the earth warm), and 
outside of this there is nothing at all. 

We must have a name for this empty 



34 THE EARTH AND SKY. 

space — for this space where there is nothing 
at all. Let us call it just — space. Space is 
everywhere. The earth seems to float in 
space just as a balloon floats in the air, just as 
a cork floats in the water. 

Suppose you had a wonderful gun that 
could shoot a bullet that would never stop, 
but which would go on forever. If you shot 
the bullet straight up in the air it would go 
on and on quite through the air, ten miles up, 
fifty miles up, a hundred miles, till finally the 
bullet had left the earth and all the air behind 
it, and had come into what we call space. It 
would still go on. There is nothing there to 
stop it. And it would go on forever — our 
bullet. So far as we know it would go on 
and on, and on, forever. What is to stop it ? 
There is no outside to space. It is all inside. 

If you held your magic gun straight up the 
bullet would go on forever in that direction. 
If you held it nearly level, pointing to the east, 
and shot another bullet, that one, too, would 
go on and on forever, through the air, and out 
beyond it into space, and on, and on, and on. 



THE EARTH IN SPACE. 35 

What is to stop it ? And if you shot another 
bullet to the west, and another to the north, 
and another to the south — all these bullets, 
too, would go on through the air — out beyond 
it, and on, and on, forever. What is to stop 
them \ 

This picture might show Master Frank 
standing at F and pointing his magic gun up, 
or to the east, or to 
the west, or any- 
where, and shooting 
magic bullets out 
through the air into 
space. No matter in what direction you shoot 
them, they will go on forever. There is noth- 
ing to stop them. Space goes on forever in 
every direction, no matter which way you 
point. 

If you should take your magic gun to San 
Francisco, or to Asia, or to Cape Horn, or 
to the arctic regions, or anywhere, and if you 
should shoot a shower of magic bullets in every 
direction, from every one of these places, each 
one of these bullets would go on and on for- 




^^ 



36 THE EARTH AND SKY. 

ever with nothing to stop it. Space is every- 
where, in every direction, and it lias no end. 
Did you ever think of this, Master Frank ? 
Space is like an endless ocean of nothingness, 
and the earth is floating in one little part of it. 

We said the earth was very large just now 
when we were talking about it. And so it is. 
It is much larger than many Franks, much 
larger than many New Yorks, much larger 
than many Americas. But what a very little 
speck it is inside of this huge, immense, gigan- 
tic space in which it floats ! You could walk 
round the earth in seven or eight years we 
said. But seventy lifetimes of walking would 
not take you far into space. Suppose your 
magic bullet went a mile in a minute, which is 
as fast as the fastest railway trains, it might go 
on and on for ever and never come to the end 
of space, no matter which way you shot. 

One of the wise men of old times * was 
once talking about space. Sonier one said that 
space had an end to it — that space had a 
limit — a boundary. On this side of the limit 

* Lucretius. 



THE EARTH IN SPACE. 37 

there was space ; on the other side no space. 
" Well," said Lucretius, " I stand at the limit 
with my lance, and I throw my lance outward. 
Where does my lance go ? " Of course his 
lance would go into space, and of course there 
was no such limit to space at all. Space is 
everywhere and contains everything. It has 
no boundary. The earth and all of us on the 
earth are floating in space. The sun, the moon, 
and all the stars are floating in space. 



CHAPTEE V. 



THE SOT. 



Now, Master Frank, the question is, Have 
we any neighbors in this ocean of space ? Tell 
me if you know of any other things beside the 
earth that are floating about in space. "Well, 
there is the sun?" "Yes, there is the sun; 
that is one neighbor." "And there is the 
moon." "Yes, the moon; another neighbor." 
" And the stars." " Yes, more neighbors, mil- 
lions of them. Are there any more that you 
can think of? No more? Well, you have 
thought of nearly all of them. The sun, the 
moon, and the stars are our neighbors." They 
are not very close ones. They are very far 
away ; but they are all the neighbors we have. 
They are all of them floating in space just as 
we are. What shape is the earth ? We found 

38 



THE SUN. 39 

it was a globe, you know. Well, the sun is a 
globe, too — a globe of the same shape as the 
earth, only very, very much larger. 

How can you know that the sun is a globe ? 
Suppose you wait for a foggy day and then 
look up toward the sun. You can see it 
through the fog, and you can see its shape. It 
is quite round. At sunset and at sunrise, too, 
it is round. If you take a piece of common 
window glass and hold it over the flame of a 
candle, and smoke it evenly all over, you can 
look at the sun through it. Only you must be 
careful not to hurt your eyes. 

You will see that at any and at every time 
of dav the sun is round. Now, a thin^ that al- 
ways looks round, as the sun does, no matter 
when or where you look at it, is probably a 
globe. And the sun is a globe, as I will show 
you in a different w r ay some day. Not only is 
it round, but it shines with its own light as an 
electric light or a candle does. The sun shines 
by its own light. The earth does not shine 
at all. 

But before we go any further let me tell 

6 



40 THE EARTH AND SKY. 

you exactly how to smoke your piece of glass 
in the best way, without burning your fingers. 
You must first get the glass. Choose a piece 
about three inches square. Then borrow a 
pair of pincers from somebody, and hold the 
glass in the pincers. Do not hold it too tight 
or else you'll break the glass and spoil it. 

Now hold the glass flat over the flame of a 
candle and several inches above it, and move 
the glass about a little. The smoke from the 
candle will make a thick, black film of soot on 
the glass ; and you must keep moving the glass 
about till the film is quite thick and very 
even, with no holes in it. If the sun shines 
through any hole that a careless boy has left, 
it will ruin his eye, so you'd better be careful ! 

The very best way to smoke the glass is not 
to use a candle at all, but to use camphor in- 
stead. Buy a piece of camphor, about as big 
as a green pea, from the druggist, and put it in a 
saucer, and set it on fire with a match. It w T ill 
send out a thick smoke, which is just the thing 
for smoking glass. Hold the glass over it till 
the whole glass is covered with a thick film of 



THE SUN. 41 

soot, quite evenly, with no holes in it. Then 
you can look at the sun through it safely. 
Perhaps, to be quite safe, you may better let 
papa or mamma or Aunt Clara try the glass 
first, and when it is just right you can use it. 

You should hold the smoked side of the 
glass away from your face, and the unsmoked 
side toward your eye. " What for ? " Can't 
you guess ? So as not to get the soot on your 
nose, my boy. 

Another way to see the sun even better 
than through smoked glass is to buy from an 
optician (a man who makes or sells spec- 
tacles, and so forth) two or three pieces of 
colored glass (red is the best). If you look 
at the sun through one piece only it will be 
too bright and will hurt your eye. Let some 
of the older people try first and they can 
decide whether you will need three pieces or 
only two. You can tie the pieces together 
with strings, or fasten them with rubber bands. 

Now you have a way of looking at the sun 
safely. And when you look at it you will see 
that wherever and whenever you look, the sun 



42 THE EARTH AND SKY. 

is round. And if it always and everywhere 
looks round it is probably a globe. I will 
show you in a different way sometime that it 
really is a globe, and a very large one. 

The picture on page 43 (if you forget about 
the line across the middle of it) shows how 
the sun looks through a smoked glass. In the 
center of the glass is the round sun, which 
looks white or yellowish through a smoked 
glass or through a fog. All around it is space, 
which looks blackish through the glass. No 
light comes from empty space. If you are 
looking through a red glass the space around 
the sun will be red, and the sun itself will be 
a far more brilliant red. 

Just now I said that the sun was an ex- 
ceedingly large globe. Scientific men know 
just how large it is. Sometime I will tell you 
how they know, but you must take my word 
for it now x . It is so large that if you could 
lay one hundred globes as big as the earth 
across the sun they would not reach from edge 
to ed^e. It would take one hundred and nine 
of them to do it. 



THE SUN. 



43 



The line across the face of the sun in 
the picture is a line of one hundred and 
nine little dots. Count them. If the earth 




This picture shows one hundred and nine little black dots laid 
across the white circle. If each of these little black dots 
were as big as the whole earth, the white circle would be just 
the size of the sun. 



could be taken and put just in front of the 
sun it would be no larger than a single one of 



44 THE EAETH AND SKY. 

those little dots. Think of it ! This earth that 
we said was so large (and that is large to us) is 
only a speck alongside of the sun. It would 
take one hundred and nine earths placed side 
by side to make a line across the sun's face ! 

The sun is a globe, you know. It is solid 
and not flat like the picture. How many little 
globes like one of those little black dots do 
you think it would take to fill up the whole 
globe of the sun ? If the sun were a hollow 
globe w r ith a hole in the top how many earths 
would you have to drop in through the hole 
before the hollow globe of the sun was filled ? 

You can see that thousands and thousands 
of earths would be needed. I will tell you 
that it would take more than a million of 
them — more than a thousand thousands of 
them. Think of it — first there is one earth — 
then a heap of ten earths — then a hundred 
such heaps. Let us imagine all these hundred 
heaps put into one large pile. 

Now we have a thousand earths in a huge 
heap. We should have to make a thousand of 
such heaps in order to get enough to fill up the 



THE SUN. 



45 



hollow globe of the sun. You can see from the 
picture on page 43, which is a true one, that it 




would take very many of the little black dots 
to fill up a hollow globe as large as the white 
circle. 



46 THE EARTH AND SKY. 

Great as the earth seems to be the sun is 
immensely greater; and even the sun is the 
merest speck in comparison to space. 

The picture on page 45 is worth looking 
at, Master Frank. It is a drawing that shows 
how the sun looks in a small telescope ; and 
down at the bottom of the picture is a little 
white dot which shows how large the earth is 
in comparison with the sun. 

It is another way of showing how vastly 
larger the sun is than this earth on which we 
live. On the sun's face are some dark spots — 
sun-spots they are called — which I shall tell 
you about some day. Notice that some of 
them are very much larger than the whole 
earth. The sun has spots on his face bigger 
than the earth ; and those are only the spots ; 
what an enormous face ! 



CHAPTEE VI. 
THE moon. 

One of our neighbors in space is the sun. 
Another one, our nearest neighbor in fact, is 
the moon. You have heard that the sun is a 
huge globe, and that it shines by its own light 
as an electric light shines. The moon is a 
large globe, too, not so large as the earth, but 
still very large. The moon does not shine by 
its own light. It simply reflects the sunlight, 
just as a mirror would reflect an electric street 
lamp w T hich shone on it. Whenever the sun 
shines on any part of the moon it is daytime 
on that part, just as it is daytime on the 
earth wherever the sun is shining. 

A few pages back we had a picture show- 
ing how very large the sun was compared to 
the earth. It would take more than one hun- 

47 



48 



THE EARTH AND SKY. 



dred earths put side by side in a straight line 
to reach across the sun's face. This picture 

shows that the earth 
is very much larger 
than the moon, but it 
would not take one 
hundred moons side 
by side to reach 
across the earth's face. 
Three moons side by 
side in a line would 
not quite reach across. 
Four moons side by 
side would be enough. 
It is a little less 
than eight thousand 
miles through the earth in a straight line from 
side to side. And it is a little more than two 
thousand miles through the moon, from out- 
side to outside again. You see the moon is 
certainly a large globe. It is two thousand 
miles through, and more than six thousand 
miles round. A string that was long enough 
to go round the moon's globe once would be 




Comparative sizes of the earth 
and the moon. 



THE MOON. 49 

more than six thousand miles long. If you 
should cut the string in two in the middle each 
one of the parts would still be long enough to 
reach from New York to San Francisco. 

Here is a picture. I wonder if you know 
what it means ? We are talking about the 
moon, you remember. Now what has this 
picture got to do with the moon ? Oh, you 
recollect now. The moon is sometimes a thin 
sickle-shape, like the upper left-hand picture. 
You have seen it so in the early evening just 
after sunset. Yes, that is the new moon. The 
thin sickle (we call it a crescent) is the " new " 
moon, and the rest of the dusky circle we 
call " the old moon m the new moon's arms." 
You've heard them spoken of in that way, 
haven't you ? Now look at the upper right- 
hand picture. The sickle is much fuller, but 
you can still see the old moon. 

In the third picture the moon seems to be 
cut exactly in two. The bright part that you 
see is just half of a globe. The other half seems 
to be quite gone. There is no light there. 

In the fourth picture the blight part has 



50 



THE EARTH AND SKY. 
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THE MOON. 51 

grown larger — much larger. And in the fifth 
picture the moon has grown to be quite round. 
It is all bright and it is round. That is what 
is called a " full " moon. You can see the full 
moon rising in the east, just as the sun is set- 
ting in the west, once in every month. In the 
sixth picture the moon is of an oval shape, not 
round, and only part of it is bright. In the 
seventh there is a half moon again, just as 
there was a half moon in the third picture, 
only the bright part is turned a different way. 

And in the last picture of all there is a 
broad sickle (or crescent), like the crescent in 
the second picture, only it is turned another 
way. 

What is the meaning of all these pictures ? 
It is such a pity that we have to study the 
moon from pictures, you and I. It would be 
so much more simple if we could go together 
out into the night and look at the moon our- 
selves. 

But if we can not do this together, you can 
do a great deal of study by yourself. It will 
only take a little time every night for you to 



52 THE EARTH AND SKY. 

make a drawing of the way the moon looks 
(that is, if the night is clear and you can see 
the moon at all). 

It will be a very useful thing if you can do 
this. And it will be quite interesting too. 
Let me tell you how you can do it in the best 
way. You must get a little blank book, and it 
will be a good plan for you to borrow a silver 
half dollar from your father. The book is to 
make your drawings in, and the half dollar is 
to make circles with. 

In the first place, what is it you want to 
learn by making these drawings ? You know 
already that the moon is sometimes a full 
circle, and that sometimes it is a crescent — 
a sickle ; but you can not tell me, now, 
exactly when these changes happen, nor ex- 
actly why they happen, so that you need to 
make these little drawings day after day to 
find out when the changes come. After you 
know when they come, perhaps we can find 
out why they come. At any rate, your draw- 
ings will tell you when they come, and so 
much will be gained. 



THE MOON. 53 

Suppose you make one drawing of the 
shape of the moon every day that you can ; 
and suppose your little book has fifty or sixty 
pages in it. Some days it will be cloudy, and 
you can not see the moon at all. There will 
be no drawings for those days, of course. And 
on some days the moon will rise in the east 
after you have gone to bed, and w^hen you are 
fast asleep. So on those days, too, there will 
be no drawings. Never mind. You are onlv 
asked to do the best you can. 

Just remember to look for the moon in the 
sky every night and every day. If you see it 
you must draw the shape of it. You need not 
draw anything except its shape. Do not try, at 
first, to draw anything but the lines that are 
round the bright part of the moon ; not any 
spots or dark places on it. Just the shape. 
We are trying now to find out why its shape 
changes. 

Suppose you begin in this way. You go 
out of doors and look round in the sky for the 
moon. Sometimes you can not find it at all. 
Sometimes you mil see it in the night-time. 



54: THE EARTH AND SKY. 

Sometimes you will see it in the daytime. 
Very well. All you have to do is to put 
down in your little book just wliat you see. 
If you see nothing at all you are to put that 
down, too. 

Every leaf of your little book belongs to 
a day. One leaf for every day. Suppose that 
you see the moon on Tuesday, the 1st of 
March, at six o'clock in the afternoon. Look 
carefully at the shape of the moon. Is it 
round or is it sickle-shaped ? Which way 
do the two horns of the sickle (the cres- 
cent) point — towards the sun or away from 
the sun ? If the sun has set you can at least 
tell whether the horns point eastward or 
westward. 

Now, have you made up your mind which 
way the horns point? Have you made up 
your mind what the shape of the moon is 
to-day ? If you have, you can begin to make 
your first drawing. Begin by laying the half 
dollar down on the middle of the first page, 
and take a sharp pencil and make a whole 
circle with it all round the half dollar. 



THE MOON. 




You must hold the book open before you. 

You must always face toward the south. The 

right hand side of the 

page will be toward 

the west. Put a W 

there, then, to stand 

for west. The left 

hand side of your page 

wdll be toward the east, 

so put an E there to 

stand for east. And you had better write top 

and bottom too, as in the picture. 

You are ready to draw in the shape of the 

moon so soon as you have made up your 

mind what the 
shape really is. 
Look hard and see 
what the shape is 
and remember it, 
and then draw it 
in this way. 

That is, you are 

to draw the line inside the circle you made at 

first, so that the shape is as near the shape of 




56 THE EARTH AND SKY. 

the inoon as you can make it. Suppose it is 
like this figure. Then if you can see the sun, 
or if you know by the light of the sky pretty 
nearly where the sun is, you can draw an 
arrow which points from the moon towards 
the sun. If you do not know where the sun 
is, leave out the arrow. 

Now you have finished the drawing ; but a 
drawing of this sort is not of much use until 
it has a date to it. You must write on the 
page first j the year — if it is 1898, write it 
down. Then you must write the day of the 
week — if it is Tuesday, write that. Next 
you must write the day of the month — as 
March 1st. And then you are to write down 
the time of day — as six p. m. (six in the after- 
noon) or whatever the hour is. You can take 
the time from a watch, and you need only to 
write down the hour. Never mind the minutes 
now. 

When all this has been done, there is one 
more thing to do. You must write your 
initials at the bottom of the page. You must 
sign it. Write down F. D., if those are your 



THE MOON. 57 

initials. This means that you have made the 
best drawing that you can ; that it is right 
so far as you know ; and that yon are respon- 
sible for it. Every good drawing should 
be signed. And if your first drawing is not 
good, you must make another one that is good, 
and sign that one. 

So, every day you can make a drawing, the 
best drawing possible. And you must remem- 
ber to put in the year, and the day of the 
week; the month and the day of the month; 
the hour of the day (this tells whether it is 
daylight or dark, you know) ; and finally you 
should sign the page. And always recollect to 
face the south when you are making the sketch. 

On some days the sky will be cloudy and 
you can not see the moon. Use a page of 
your book for this day just the same, and 
write, " Cloudy — no moon seen," and sign the 
page. And on some days it will be clear 
weather and yet no moon can be seen w T hile 
you are awake. You should take a page of 
your book for such days too, and write, " Fair 
— no moon seen," and sign that. 



58 THE EARTH AND SKY. 

But whenever the moon is to be seen 
during the hours that you are awake, either 
in the daytime or at night, you should mate 
a drawing of its shape as well as you can ; 
and you should write down the year and 
month, and clay of the month, and day of 
the week, and the hour, and sign the page 
Signing it means, "I have done the best I 
can, and the page is right as nearly as I can 
make it." 

You must not mind, Master Frank, if your 
drawings are not exactly right at first- All 
you have to try for is to make them as nearly 
right as you can. That is all anybody can do — 
to do as w r ell as he can ; to take pains ; to be 
patient about it. 

Finally, you will have your book filled. 
Some of the pages will have no drawings, be- 
cause the night (or day) was cloudy. Some 
of the pages will have no drawings, although 
the night (or day) was fair. Very likely 
Master Frank was sound asleep when the 
moon was overhead, shining. But you will 
have a number of drawings, anyway. And 



THE MOON. 



59 



each one of them will give the shape of the 
moon as well as you can draw it. 

It has taken a good many days — fifty or 
sixty — but you have done the best you knew 
how to do, and you have a number of draw- 
ings of the shape of the moon. That is, of the 
shape the moon had on those particular days. 

Top. 



E. 



*#• #CC 



> /7*S 



5 

Bottom. 



8 



The bright part of the moon goes through changes like these 
every month. You first see it as a new moon in the west 
about sunset like No. 2. It is full moon when the shape is 
like No. 5, and so on. 

If you have been successful you may have a 
number of drawings like Nos. 2, 3, 4, 5, 6, 7, 8, 
in the picture. Never mind about Nos. 1 and 
9. Forget them just at this minute and let us 
think about the others. 

You will have, perhaps, a drawing like No. 
2. The horns of the crescent are turned away 
from where the sun was. The drawing was 
made sometime near sunset. The moon was a 
new moon, as we say. About four, five, or six 



60 THE EARTH AND SKY. 

days later than this drawing you will probably 
have a drawing in w r hich the moon looks some- 
thing like the moon in No. 3 of the picture. 
It is a half moon. There may be a drawing 
like No. 4 three or four days after the day 
of the half moon. 

You must be careful not to mistake a 
moon like No. 4 for a moon of the shape of 
No. 6. There is a difference, you see. The 
bright part of No. 4 is toward the west The 
round part of No. 6 is toward the east Be 
careful not to mistake a moon like No. 3 for 
a moon like No. 7. The bright half of the 
moon in No. 3 is turned toward the west. 
The moon in No. 7 has its bright half turned 
away from the west. Very likely you may 
not see a moon of the shape of No. 7 at all. 
If you do see it you will see it very late at 
night, or else in the daytime and in the west, 
after you have had your breakfast probably. 

Sometime, if the weather is fair, you will 
see a full moon like No. 5. It will be of this 
shape about a week after the half moon of No. 
3, and about a week before the half moon of 



THE MOON. 61 

No. 7. Talking about these pictures is not 
nearly so good as really seeing the moon in the 
sky, and talking about the real moon. But it 
is the best we can do ; and if you have made a 
good set of drawings we shall understand each 
other at any rate. 

Well, you have arranged all your drawings 
in order and you have a set of pictures like the 
last figure, or like the eight pictures in one 
group of the picture on page 50. (Turn back 
and look at it, please.) 

You know now that the moon changes its 
shape from night to night. You knew that 
before, but you know it better now, for you 
have taken pains to know. And you know 
pretty well when it changes. That is, how 
many days it takes to change from one shape 
to the next one. That much you know for 
yourself. The next thing is to try to find out 
why all this happens. 



CHAPTEE VIL 

WHY THE BKIGHT PAET OF THE MOON CHANGES 
ITS SHAPE FEOM NIGHT TO NIGHT. 

See if you can find among the drawings 
you made of the shape of the moon two that 
are alike. If you can, you will find that one 
was made just about a month later than the 
other. If the moon was "full" on April 10th 
(for example) it will be " full " again about 
May 10th, a month later. Every month there 
is a full moon and the next full moon comes a 
month later (to be exact, it comes twenty-nine 
days later). In fact, the month was invented 
ages and ages ago, by the men of early times, 
so that it should be just long enough to take 
in the changes of the moon. 

At the beginning of a " lunar " month (a 
moon month) there is no moon to be seen at 

62 



WHY THE MOON CHANGES ITS SHAPE. Go 

all. It is just before "new" moon. (Look at 
No. 1 in this set of nine pictures.) The very 
first sight of the "new" moon (No. 2) comes 

Top. 



)3ltiC( 



; ■■■■BB ,M jM ill W^KJh W. 



oc 



5 

Bottom. 



about sunset. The sun is just setting, or has 
just set, and you see the faint crescent moon 
in the western sky. Its round part is turned 
toward the sun, and its two sharp horns are 
turned away from it. 

The bright crescent grows wider and wider 
and a few days later you will see that the 
shape of the moon is just half a circle (No. 
3). Then the circle changes into an oval like 
No. 4, and finally into a full circle like No. 5. 
This is the "full" moon and it comes about 
fifteen days after the beginning of the " lunar " 
month, or about twelve or thirteen days after 
the day on which the " new n moon is first 
seen. 

The full moon always rises in the east 
just about the time that the sun is setting in 



64 THE EARTH AND SKY. 

the west. They are opposite to each other, 
and the sun is shining full on the face of the 
moon, and we are seeing the whole of the face 
that is shined upon. After full moon the 
shape changes, as you know. The " old " moon 
gets to be oval again, like No. 6, and then it 
gets to be a half moon once more of the shape 
shown in No. 7. Only this half moon has its 
round side turned to the eastward. The other 
half moon that came soon after new moon (No. 
3) had its round side turned toward the west- 
ward. 

By and by, in the late night or early morn- 
ing, you can see the moon a sickle again- — 
a crescent — like No. 8. And this sickle will 
have its round side turned eastward. The 
" new " moon (No. 2) had its round side turned 
westward. The round side is always turned 
toward the place where the sun is. The sun 
is shining on the moon on that side and is 
making it bright. 

Month after month these things happen, 
and the moon's shape changes. Twenty-nine 
days after one new moon comes the next new 



WHY THE MOON CHANGES ITS SHAPE. G5 

moon. Twenty-nine days after a full moon 
comes another full moon, and so on forever. It 
has always been so as long as men can remem- 
ber ; and it will always be so for ages to come. 

The reasons for these changes are not very, 
very hard to understand though they are not 
really easy. You must remember four things 
that I am going to tell you. In the first 
place, the moon does not shine by its own light. 
It is just a globe of rocks which the sun shines 
upon. The half of this globe which is turned 
toward the sun is lighted up — is bright. 

In the second place, the moon moves round 
the earth in a circle, far away from us, but 
always at the same distance. In the third 
place, it takes the moon twenty-nine days to 
go once round the circle. It starts from a 
point in the circle and it moves round the 
earth, and twenty-nine days later it comes 
back to the point it started from. It doesn't 
stop there, of course, but keeps right on, and in 
another twenty-nine days it has gone round the 
circle again, and so on. The circle is not near 
to the earth. It is very far away. 



66 THE EARTH AND SKY. 

And the fourth thing to remember is that 
you are on the earth watching the far-away 
moon in the sky, and seeing only one side of it. 
You are seeing the half of the moon that is 
turned toward you. Sometimes that half is all 
bright. Sometimes it is only partly bright. 

Look at this picture now, Master Frank, 



W THE 
'£ SUN 


^L Ma^H 


M 7 


^A Here intervenes / \ 
■ Mi] ^ 
H a space equal .(H m 

^m to about 190 times \ / 

^f the distance M, M 5 \f 


7 Q 5 

*3 



This picture shows why the bright part of the moon shows differ- 
ent shapes to us on the earth at different times of the month. 
The sun is at the left hand side of the picture. It is shining 
on the earth and the moon at the right hand side. The earth 
is the globe in the center of the circle, M is the moon. It 
shines on one half of the earth, and makes day-time. It 
shines on one half of the moon — on that half turned toward 
the sun. We who live on the earth can see only the half of 
the moon turned toward us. So that we see the moon of 
various shapes. 

and see what it means. The sun is on the left 
of the picture and you must imagine it to be 
shining. It sends out sunlight and shines on 



WHY THE MOON CHANGES ITS SHAPE. Q7 

everything on the earth and makes the day- 
time, and on the moon and makes the bright 
moon that we see. It is very far away. 

Noav, in the picture you must find the 
little globe in the center of the circle of Ms. 
That is meant to be the earth. We have to 
draw it very small, you know. Let us call 
it E. 

E is the earth and one half of it is bright — 
the side turned toward the sun ; and the other 
half of it is dark — the side turned away from 
the sun. It is daytime where the sun shines, 
isn't it ? Well, then, the left-hand half of that 
little globe E, the earth, must be in the day- 
light; and it must be night on the right-hand 
half of the little globe in the picture. 

Round the earth E there is a circle wdth 
eight little globes, M 1? M 2 , M 3 , M 4 , M 5 , M G , M r , 
M 8 , on the circle. The circle is meant to show 
the path in which the moon moves round the 
earth, and the eight little globes are meant to 
show eight of the places where the moon will 
be in the course of a month. If the moon 
is at Mi at the beginning of a month, it will 



68 THE EARTH AND SKY. 

move to Mo in about three and a half days. 
In three and a half days more it will move to 
M 3 , and in three and a half days more to M 4 , 
and so on. 

In just half a month — in fourteen and a 
half days that is — it will move halfway round 
the circle to M 5 , and in the rest of the month 
it will move over the rest of the circle to M 1# 
Just a month after it left M t the moon will get 
back to M} again, and so on. Now let us look 
at one of the little globes on the circle. Let 
us begin with M^ 

You see that this little globe, M l9 has one 
half bright and one half dark. The half that 
is turned toward the sun is bright. It is day- 
time on that half of the moon, and it is night- 
time on the other half of that moon M l7 be- 
cause the sun is not shining on that half. 

The daytime side of the moon M t is turned 
toward the sun. The night-time half of the 
moon Mj is turned toward the earth ; and the 
people on the earth, you among them, can not 
see the moon, of course. There is nothing to 
see it by. All the sunlight is on the other 



WHY THE MOON CHANGES ITS SHAPE. 69 

side — on the farther side — on the side turned 
away from you. The moon is not seen by peo- 
ple on the earth w T hen it is on a line from the 
earth toward the sun. 

Now let us look at another of the little 
globes in the picture. Let us take M 3 , the 
picture at the bottom of the circle. The sun 
is shining on the left-hand half of the globe 
of the moon at M 3 , and making that left- 
hand half bright. The right-hand half will 
be dark, of course, because the sun does not 
shine upon it. Now how will the moon at 
M 3 look to you? Recollect that you are a 
little speck on the earth at E, and that you 
are looking out toward the moon in the sky 
at M 3 . You are looking along the line E to 
M 3 ; from E toward M 3 . If you look along 
any other line you will not see the moon, 
because the moon is at M 3 and nowhere else. 

The left-hand half of the moon at M 3 is 
bright, and the right-hand half of the moon 
is dark. How will it look to you ? Imagine 
yourself standing up on E — the earth — and 
looking at M 3 . Your back wdll be turned to 



70 THE EARTH AND SKY. 

the top of the page and you will be looking 
downward on the page along the line from E 
to the moon at M 3 . You will see the moon 
half bright like No. 3 in the picture on page 
63. The bright half of the moon will be on 
the right-hand side and the left-hand side will 
be dark. 

Now let us look at another one of the 
little globes. Take M 5 this time. The sun 
is shining on the left-hand half of M 5 and 
making it bright. (The sun shines below the 
earth at E. It shines past it. The earth is 
not really placed so as to stop the sun's light, 
though the last picture has to be drawn as if 
it were so.) 

The sun lights up the left-hand half of 
the moon at M 5 and makes it bright; and 
you are standing on the earth at E, looking at 
the moon at M 5 , along the line from E toward 
M 5 . This time your back is toward the sun, 
your face is toward M 5 , and your eyes are 
looking along the line from E to M 5 . The 
half of the moon that is turned toward the 
earth — toward you — is all bright. Therefore 



WHY THE MOON CHANGES ITS SHAPE. 71 

you will see the moon all bright — full moon — 
as in No. 5 of the picture on page 63. 
When you stand on the earth, with your back 
to the sun, and see the moon just opposite to 
you, it will be a full moon. 

Now you must study the last two pictures 
for yourself carefully, Master Frank. You 
may better take a pin for a pointer and study 
each one of the little globes by itself, just as 
we have studied the moon at the two places 
M 3 and M 5 . 

Put the pin on the earth at E in the pic- 
ture. You are standing there, looking out at 
the moon in the sky. When you look out 
along the line from E to M 2 , for instance, what 
do you see ? The left-hand half of the moon 
at M 2 is shined upon by the sun. The right- 
hand half is dark. As you look you will see 
the shape of the moon like No. 2 in the last 
picture but one. 

If you look along the line from E to M 4 
you will see the moon like No. 4 ; if you look 
along the line from E to M 5 , it will be like No. 
5, and so on. You may better try each one of 

8 



72 THE EARTH AND SKY. 

the different places, M 6 , M 7 , M 8 , and you will 
see that the moon in those places will look like 
Nos. 6, 7, and 8 in the last picture. 

Now you can see why it is that the bright 
part of the moon changes its shape from night 
to night. The real moon is always of the same 
shape, of course. It is a globe. The sun 
shines upon it and lights one half of it only. 
It lights the half that is turned toward the 
sun, of course. You are standing on the earth, 
and when you are looking at the moon you 
see it sometimes of one shape and sometimes 
of another. 

Sometimes the bright part of the moon is 
a crescent — a new moon. That is because you 
are looking toward the sun. You can not see 
the whole of that part of the moon that the 
sun shines upon. Sometimes the bright part 
of the moon is quite round — a full moon. 
That is because you are looking away from the 
sun and because you are looking at exactly the 
same half of the moon that is lighted up by 
the sun. The sun lights all of one half, and at 
full moon you see all of that half. The sun 



WHY THE MOON CHANGES ITS SHAPE. 73 

always lights one half. But you sometimes 
can not see the whole of the lighted half, but 
only a part of it. 

You, of course, are always on the earth, 
and nearly always in the same place — in the 
same city. But the moon does not stay in the 
same place. It moves round the earth in a 
circle (it is about a half million miles across 
that circle). 

Do you understand now why it is that the 
bright part of the moon has different shapes at 
different times ? I hope you do, and I think 
that you do. But if it is a little too hard to 
understand you may better go on and read the 
next chapter of this book about the stars. 
And afterward you can read this chapter over 
again very carefully, and perhaps you can get 
some older person to read it with you. Of 
course it takes trouble to understand any sci- 
ence like astronomy. The world is not simple. 
But if you take pains, and go slowly, and have 
patience, you can understand very much. There 
is no hurry anyway, is there ? There is plenty 
of time ; and you have got all the time there is. 



CHAPTEE YIIL 

THE STAES IN THEIR COURSES — THE EARTH 
TURING ROTTED O^CE I1ST EVERY DAY. 

All the day the sun is shining and making 
daylight. By and by comes sunset and the 
sun has gone below the horizon — below the 
rim of the world — in the west. He leaves the 
clouds and the sky bright and you can see only 
a very few stars — only the brighter ones. 

The sky now begins to get darker and 
darker, and little stars begin to peep out here 
and there. In an hour or less after the sun 
is set the whole sky is quite dark (unless, per- 
haps, the bright moon is there) and you can 
see hundreds and hundreds of stars. The 
sky is full of them. Some of them are very 
bright indeed, some are much fainter, and 
some you can scarcely see at all. But they are 
there — little, bright, twinkling points. 

74 



THE STARS IN THEIR COURSES. 75 

We could not see the stars in the daytime, 
an hour before sunset, for example, because 
the sun's light was so bright. The daylight 
made the whole sky so bright that the stars, 
which were there all the time, couldn't be seen. 
The stars are in the sky all the time. We 
do not see them in the daytime simply because 
the sky is so bright that the strong daylight 
blots out the feeble light of the stars. 

Make a little dot of ink on a piece of 
paper. Now take the end of a match and 
make a blot over the little dot. The dot can 
not be seen any more. But it is there all the 
time, under the blot. Just in the same way 
the light of the day blots out the light of a 
star. 

We know for certain that the stars are 
there, shining in the daytime, though your eye 
can not see them, because astronomers can see 
them in their telescopes. They can see them, 
and they often and often do see them, and if 
you could look into their telescopes you could 
see the stars in the daytime too. 

As the sun sets the sky gets darker. Only 



76 THE EARTH AND SKY. 

the very brightest stars can be seen just then. 
Such stars must be brighter than the sky in 
order that you may see them at all. And so, 
of course, the brighter stars will be the first 
to be seen after sunset. And the farther 
away from the sun you are looking just after 
sunset, the more stars you will see. Because, 
of course, the sky is darker farther away from 
the sun, and a star that will show plainly on 
this dark sky may be too faint to be seen 
close to the sun. 

All the stars, you know, shine by their 
own light, just as the sun shines by his own 
light. They are not like the moon which has 
no light of its own, but they are like the sun ; 
and each one of them shines by its own light. 
If you could hide the sun's light all the stars 
would go on shining just the same ; but if the 
sun's light was really hidden — if the sun was 
blown out like a candle — the moon would 
never shine ag;ain. 

All the moon's lig;ht comes from the sun. 
Each star has a light of its own. If you want 
the stars put out, you must put them out one 



THE STARS IN THEIR COURSES. 77 

by one like separate candles. If yon want 
the moon put out you can only have it by 
blowing out the sun. 

When you are looking up at all the stars 
in the dark sky what do they look like? 
They appear like bright shining sparks fast- 
ened on to the inside of a huge hollow half 
globe. We are standing in the middle of this 
globe on the solid earth. All round us and 
above us is the immense globe of the sky, like 
a huge basin. 

Look off to the north, or to the east, or to 
the south, or to the west; in every direction 
you can see that the bowi of the sky is very 
larw indeed. It seems to come down and 
meet the ground all around the horizon. Lie 
down on your back and look straight over- 
head, and you can look on and on, ever so far ; 
but by and by you seem to come to an end, 
and you seem to have reached the hollow bowl 
of the sky. In every direction you will find 
the same thing. In every direction there seems 
to be a huge bowl above us and around us. 

On the inside surface of the bowl the stars 



78 THE EARTH AND SKY. 

seem to be fastened like little shining sparks — 
some bright, some fainter. So, when you think 
of it, the stars seem to be — they appear to be 
— all at the same distance from yon. They all 
seem to be fastened on the inside of the great 
hollow bowl. 

But the stars are not all at the same dis- 
tance from you by any means. Far from it. 
All of them are very far away indeed. All of 
them are much farther away from you than 
the moon is, or than the sun. But some of the 
stars are ten times farther off from you than 
the nearest stars. Some are a hundred and 
others a thousand times farther off from you 
than these nearest stars. 

If this is so — and I will some day prove to 
you that it is so — then it is plain that all of 
the stars can not be fastened on the inside sur- 
face of a great bowl. They certainly look as 
if they w r ere fastened that way. But they can 
not be so fastened. No one bowl would do. 
The near stars and the farther stars could not 
be fastened to the same bowl. 

So that it is not a true appearance, this 



THE STARS IN THEIR COURSES. 79 

bowl of the sky. It looks as if there were 
such a bowl, on which all the stars are fast- 
ened. But there certainly is no such bowl. 
It is all a mere appearance. Let us see how it 
happens to look like that. 

Here is a picture, and in the middle of it 
is a white dot marked O. That white dot is 




supposed to be the earth, and you are on it, 
looking out at the stars in the dark night. 
p, q y r 7 s, t, t, t, u 9 v are stars at different dis- 



80 THE EARTH AND SKY. 

tances from you. The star p is farther away 
from than the star q. 

If you look at the star p from you look 
along the line p P, and you seem to see the 
star p at the place P on the inside of the hol- 
low bowl. If you look at the star q you look 
along the line q Q, and you seem to see the 
star q at Q on the inside of the hollow bowl. 
If you look at the stars r, s> % v, along the 
lines r P, s S, u U 7 v V, you seem 
to see them on the hollow bowl at P, S, U, V. 

Suppose there were really three stars, t, t, t, 
at different distances from you, but all in one 
line. You would only see one star. It would 
seem to be on the inside of the hollow sky at 
T. The white circle in the picture is meant to 
show what we have called the inside surface 
of the hollow bowl of the sky. 

It seems to have stars sprinkled all over it 
at P, Q, P, S, T, IT , V, and at other places ; 
and all these stars seem to be at the same dis- 
tance from you. P is just as far from O as Q 
is, as P is, etc. But the stars are really at 
different distances from you. Some of them 



THE STARS IN THEIR COURSES. 



81 



are near, like q, and some of them are far off, 
like u and v. They simply appear to be on 




This picture shows the stars in the northern part of the sky as 
they look in the early evening in midsummer. All of the 
stars move round the sky from east to west — from rising to 
setting — once every day. The Pole Star alone stands still. 
The Great Dipper (marked Ursa Major in the picture) moves. 
Two of its stars, the Pointers, always point to the Pole Star. 

the hollow sky, and the hollow sky itself is 
nothing but an appearance. Remember that. 
Here is a picture of a part of the sky, 



82 THE EARTH AND SKY. 

Master Frank, from which you can learn other 
new things. No one picture can show the 
whole sky ; nor can any one picture do more 
than to show a part of the sky at some particu- 
lar month and day and hour. The stars rise 
and set like the sun and moon, you know. A 
picture will only serve to show the stars as 
they are at some particular hour after they 
have risen, and before they, have set. If we 
want a view of them at some other hour we 
must make another drawing. 

This picture is drawn to show the stars in 
the northern sky as they stand in the early 
night-time in every August, If you compare 
it with the stars in the sky in some other 
month it will not agree exactly, but it will not 
be hard for you to find the groups of stars at 
almost any time. The very first group of stars 
to find is the great Dipper. (See page 83.) 

Here is another picture which shows eight 
stars. Seven of them make the Dipper, and 
the other one is the pole-star. It is at the 
north pole of the sky, and it has a special 
name, which you must fix in your memory. 



THE STARS IN THEIR COURSES. 83 

Its name is Polaris. Polaris is the pole-star, 
or the north star. The stars of the Dipper are 
part of a group that is called the Great Bear 
( Ursa Major in Latin), and they are named 
by Greek letters, as in the picture. But you 
need not learn the Greek letters. They are 




Ursa Major and Polaris. 

the first seven letters of the Greek alphabet : 
a {3 7 8 e f t] 
You can find the seven stars of this picture 
in the picture that is printed on page 81. 
They are on the left-hand side of that picture. 
You can easily find them in the sky on any 
clear night. They are pretty bright ; they are 



84 THE EARTH AND SKY. 

in the north somewhere, and they are almost 
always to be seen if the sky is clear. 

In the northern parts of the United States 
they are rather high up in the sky. As you 
go farther south they get to be lower in the 
heavens, but you can always see the two Point- 
ers, a and /3, in Virginia and in North Carolina, 
and in all the States as far north as these. 
These two stars — the two Pointers — have a 
line drawn through them in both pictures. 
The line drawn through them points to Po- 
laris, the pole-star, and they get their name for 
that reason. 

The line through the Pointers always 
points to Polaris. In the last picture the 
two Pointers are just below Polaris, and the 
line points upward. In the larger picture the 
line of the two Pointers is shown pointing to 
the right (as it does in August). 

No matter what the time of year, or 
month, or day, may be, no matter what o'clock 
it may be, the line through the two Pointers 
points to the pole-star, Polaris. Every time 
you go out of doors on a clear night you can 



THE STARS IN THEIR COURSES. 85 

see that this is so. And you may better get 
into the habit of glancing up at the northern 
sky to notice this. It is always so, and you 
can prove it at any and every time you wish. 

The first thing for you to do is to learn to 
find the Dipper quickly. Very likely you 
know how to do this already. At any rate, 
you can soon learn. There is the handle of the 
Dipper, made out of three stars (e, f, y in the 
last picture), and there is the bowl of the Dip- 
per, made out of four stars (a, & y, 8). 

Two of these four stars, a and ft, are the 
Pointers. Imagine a long line drawn through 
these two Pointers ; this line will pass (nearly) 
through Polaris. You must learn, if you please, 
to find Polaris quickly in the sky. The moment 
you go out of doors at night you should see it. 

The stars a and /3, the two Pointers, always 
point to Polaris. Sometimes you will find these 
Pointers below the pole, pointing upward, as 
they are drawn in the last picture. Sometimes 
they are on the left-hand (west) side of Polaris, 
as in the larger picture. Sometimes they are 
above the pole, pointing downward. 



86 THE EARTH AND SKY. 

Hold your book upside down and look at 
the last picture and you will see how they are 
then. You can see them like that in the sky, 
too, if you look at the right time. Sometimes 
the Dipper is on the right-hand side (east) 
of Polaris, and the line of the Pointers points 
to the west. You can see it this way also, if 
you look at the proper time. 

The Dipper never changes its shape; its 
stars always keep their places, one star with 
another. But the Dipper, as a whole, moves 
round the northern sky in such a way that the 
Pointers always point to the pole-star. The 
little arrows in the larger picture show which 
way the Dipper (and all the other stars) 
move. Look at the picture carefully and re- 
member that it shows exactly what happens in 
the sky. 

Everything that w^e say about the picture 
can be proved to be true by going out of 
doors at night and by watching the stars. 
And you should do this, of course. You will 
never be truly certain that these stars do actu- 
ally move until you have seen them do it. 



THE STARS IN THEIR COURSES. 87 

Pictures with arrows in theni explain matters, 
but tlie pictures do not prove them. It is the 
other way, the stars prove the pictures. 

If you watch the northern stars you will 
find that they actually do move around Po- 
laris, the pole-star, in the direction of the 
arrows drawn in the picture. The stars above 
Polaris, those higher up, move from yotir right 
hand toward your left hand — they move from 
east toward west. The stars below Polaris 
move from left to right — from west to east. 

The eastern stars move upw r arcl, the west- 
ern stars move downward. In the larger pic- 
ture the group of stars marked Cassiopeia (the 
lady in the chair) move upward. The group 
marked Ursa Major (the Great Bear) move 
downward, and each of the other stars 
moves in a large circle around Polaris. Po- 
laris stands still and is the center of all the 
circles. 

Take the Pointer that is nearest to Po- 
laris — for example, the Pointer (a). It moves 
in a circle round the pole-star and always 
keeps at the same distance from it. The other 



88 THE EARTH AND SKY. 

Pointer (/3) moves in the same way, but in a 
different circle. , The nearest Pointer always 
keeps at its distance, a to Polaris, and the 
other Pointer always keeps at its distance, ft to 
Polaris. But both stars are continually mov- 
ing around the pole in the direction marked 
by the little arrows. 

Here is something that you ought to recol- 
lect, Master Frank. The distance of a star 
from Polaris is called the polar-distance of 
that star. Two things are true for each and 
every star: 1. Each star always has one and 
the same polar distance. 2. Each and every 
northern star moves in a circle around Polaris. 
Polaris is the center of the circle of each star. 

If you open this book to page 81, where 
the larger picture is, and hold it up before you, 
you can show how all the stars move by turn- 
ing the book and the page slowly round and 
round while you keep the middle of the page — 
where Polaris is drawn — perfectly still. 

Polaris stands still in the sky ; and there- 
fore we must keep it still in our experiment. 
The other stars all move about it in circles in 



THE STARS IN THEIR COURSES. 89 

the sky, just as we can make them move by 
turning the page round and round. While 
you are doing this you should stand up and 
you should face to the north, and it will be 
better to hold the book off at arm's length. 

In trying this experiment you have shown 
that all the stars move about Polaris in the 
same time. It takes just the same time for a 
star distant from the pole to go around its cir- 
cle, as it takes for a star near to the pole to go 
quite around its circle. The distant star has to 
move faster, of course, in order to keep up. 

Now the question is, How long does it 
take for each star to move completely round 
the pole ? The answer is that it takes just one 
day. In the picture on page 83 the two Point- 
ers, a and £, are just below the pole-star. Sup- 
pose they are like that at ten o'clock on Mon- 
day night. If you look at them at ten o'clock 
on Tuesday night you will find that they are 
in this same place again. 

It has taken them a day to move once 
round the pole-star, and they were moving all 
the time. They did not stand still for that 



90 THE EARTH AKD SKY. 

day, but they moved. You can prove this by 
watching theni. They will seem to move 
slowly enough, but they do move. We can 
now say another true thing about all the north- 
ern stars. Every star moves around the pole 
in a day. 

Long ago everybody believed that the stars 
were bright sparks set in a crystal globe — the 
hollow bowl of the sky. They noticed that all 
the stars moved round the north star (Polaris, 
the north star, the pole-star) in a day. So they 
explained this motion by supposing that the 
crystal globe turned round once every day, car- 
rying all its little sparks of stars round with it. 
They supposed that the earth stood quite still, 
and that the heavens, the crystal globe with 
the stars, turned round. 

This was a good enough explanation until 
other men found out that there could not pos- 
sibly be a crystal globe studded with stars all 
at the same distance. It was found out that 
the stars were not all at the same distance ; 
on the other hand, that they were at veiy 
different distances. Therefore there could not 



THE STARS IN THEIR COURSES. 91 

possibly be one single crystal globe for all the 
stars. 

Each one of the hundreds of stars would 
need to have a globe of its own. As it was 
not at all likely that there were as many crys- 
tal globes as there were stars, men began to 
look for another explanation. They wanted a 
simpler explanation. They found it by sup- 
posing that the stars did not move at all, but 
that the earth itself — this solid earth— turned 
round underneath the stars. 

Things would look the same, you see, in 
either case. The stars would seem to move just 
the same either way. If all the stars were set 
in one crystal globe that turned they might all 
move round with it once a day while the earth 
stood still. Or, on the other hand, the stars 
might stand still in the sky and the earth 
might move round and round and round un- 
derneath the stars. This last explanation is 
the true one. The stars are still. They really 
remain in one place. But the solid earth 
moves round and round and we move with it. 
So that the stars seem to move. 



92 THE EARTH AND SKY. 

All this time we have been speaking about 
the northern stars only. We can prove every- 
thing that has been said by watching them. 
If we should watch the southern stars what 
should we see ? Every star in the south moves 
too. It rises at your left hand (you have 
turned round with your back to the north and 
your face to the south now, you know), in the 
east, and it moves up and across the sky till it 
is halfway across. It is at its highest point 
now, and it is exactly south of you. 

Then its path leads it toward the west and 
slowly downward, and by and by it sets below 
the horizon line in the west. Every southern 
star does this. It, too, moves round a circle, 
only the lower part of its circle is hidden from 
us by the earth on which we are standing. 
The circles of the northern stars are high up 
in the sky and are not hidden by the earth. 
The southern stars (and the sun and the 
moon also) rise in the east, move across the 
sky, come to their highest points in the south 
(the sun gets to its highest point at noon), and 
decline to the west where they set. 



THE STARS IN THEIR COURSES. 93 

You must watch the southern stars too, 
Master Frank, and prove to yourself that this 
is true for them also. The more you study 
the motions of the stars in their courses the 
better you will see that their motions are fully 
explained when we suppose one simple thing 
to be true. 

We only need to suppose that the stars, 
which appear to move, really stand still, and 
that the earth is turning underneath them. 
There are many, many proofs that this is a true 
explanation. You can prove for yourself that 
it explains all the things that you see, by sim- 
ply watching the stars from night to night. It 
is satisfying to find such a simple way of ex- 
plaining so many different things, isn't it ? 
And they are all fully explained that way. 

Astronomy has many other things to ex- 
plain that are much more difficult to under- 
stand. Many of these things can not be 
understood at all until you have learned much 
more. If you want to understand them you 
must study your arithmetic hard, and you must 
understand it. Then will come a kind of higher 



94 THE EARTH AND SKY. 

arithmetic called algebra. You have to learn 
that thoroughly, and geometry as well. 

After these come other higher kinds of alge- 
bras and geometries ; and by and by you will 
have learned, in the last years of your college, 
the things that are necessary — really necessary 
— for making a study of astronomy. I mean 
necessary for studying all parts of it. 

If you wish to be able to calculate the ex- 
act time to a second when an eclipse of the 
sun will happen ten years from now, you must 
know all these arithmetics and algebras and 
geometries — all this mathematics, as it is called 
— and you must know them thoroughly. It 
takes time and hard work. But it is worth 
doing. 

And if you wish to understand whether 
human beings can possibly live in the other 
planets, in Mars, in Jupiter, in Saturn, you 
will have to learn a great deal about heat, and 
air, and so forth and so forth. If you want to 
know about telescopes, you must learn all 
about light. The study of these things is 
called physics. 



THE STARS IN THEIR COURSES. 95 

All tlie time you can be reading books 
about astronomical matters, and all tlie time 
you must be observing what you see going on 
in the sky — how the sun moves every day, 
how it moves in a year ; how the moon moves 
among the stars ; whether the moon is farther 
away than the stars or not ; where the sun 
sets in summer, and where in winter; and a 
hundred other things of the same sort. 

If you really wish to know the reasons for 
all these things, you must study physics and 
mathematics as well as you can, for all the time 
of your school, and through all the years of 
your college. Then you must study French 
and German so as to be able to read the splen- 
did books that have been written by the great 
astronomers of France and Germany. And 
you ought to know how to read Latin too, 
for in old times all the wise men wrote their 
books in Latin. 

Oh, it isn't easy, my boy ; but it is worth 
while. And you must remember one thing : 
there is no hurry about it. Walking is just 

putting one foot in front of the other, and 

10 



96 THE EARTH AND SKY. 

keeping on doing it. The boy who keeps on 
longest, who doesn't fret, who doesn't get im- 
patient, goes the farthest. It is the same way 
with learning. Every day you have to learn 
this lesson, to put this foot forward. To-mor- 
row there is another lesson to be learned, and 
another foot to be put in front. There is no 
haste, but there must not be too much rest. 

By and by, if you keep on, you will get to 
where you wish to be. If you read this book 
carefully that will be a first step. And other 
books will be other steps. Observing w^hat 
takes place in the sky itself, and thinking 
about it, so as to see why it takes place, will 
be steps that will carry you far on your way. 

And you must always remember that if you 
want any good thing in this world you must 
give something. If you want love, you must 
give love ; if you want wisdom you must give 
effort. Knowledge is not given away for noth- 
ing. You have to earn it by hard work and 
good will. 



THE SUN. 



97 




Part of a photograph of the sun, taken at the Lick Observatory. 
A sun spot is shown close to the edge. 



98 



THE EARTH AND SKY. 




Part of a photograph of the moon, taken at the Lick Observa- 
tory. (Moon's age, 16 clays 18 hours.) 



THE MOON. 



99 




5 S\ 



L ; 






Part of a photograph of the moon, taken at the Lick Observa- 
tory. (Moon's age, 8 days 1 hour.) The moon's south horn 
is shown. 



100 



THE EARTH AND SKY. 




Part of a photograph of the moon, taken at the Lick Observa- 
tory. (Moon's age, 8 days 1 hour.) The moon's north horn 
is shown. 



THE PLANETS. 



101 




Drawing of the planet Mercury. 




Map of the two hemispheres of the planet Venus. 



102 



THE EARTH AND SKY. 




Drawing of one side of the planet Mars, made at the 
Lick Observatory. 



THE PLANETS. 



103 




Drawing of one side of the planet Mars, made at the 
Lick Observatory. 



11 



104 



THE EARTH AND SKY. 




Drawing of one side of the planet Jupiter, made at the 
Lick Observatory. 



THE PLANETS. 



105 




Drawing of one side of the planet Jupiter, made at the 
Lick Observatory. 



106 



THE EAETH AND SKY. 




o 



eg 



O 

bo 



AN ECLIPSE OF THE SUN. 



107 




O 
o3 



o 

o 



00 
00 





Ha 



bo 

c3 



108 THE EARTH AND SKY. 




Photograph of the total solar eclipse of January, 1889, in 
California. 



METEORS. 



109 




Fall of the great California meteor of 1894, 



110 



THE EAETH AlS T D SKY. 



M 



11 










fcJD 




TELESCOPES. 



Ill 




The fifteen-inch telescope of the Harvard College Observatory. 
(Its glass is fifteen inches across.) 



112 



THE EARTH AND SKY. 




OBSERVATORIES. 



113 




114 



THE EARTH AND SKY. 




The six-inch telescope of the Lick Observatory, 



TELESCOPES. 



115 




The twelve-inch telescope of the Lick Observatory. 



116 



THE EARTH AND SKY. 




The forty-inch telescope of the Yerkes Observatory of the Uni- 
versity of Chicago as it was in the Columbian Exposition. 
(It is the largest telescope in the world.) 



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